import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.event.KeyEvent;


public class Snake {
	private Node head=null, tail=null;
	private int size = 0;
	private Yard y;
	
	public Snake(Yard y) {
		Node n = new Node(20, 30, Dir.L);
		head = tail = n;
		size = 1;
		this.y = y;
	}
	
	public void addToTail() {
		Node node = null;
		switch (tail.dir) {
		case L:
			node = new Node(tail.row, tail.col + 1, tail.dir);
			break;
		case U:
			node = new Node(tail.row + 1, tail.col, tail.dir);
			break;
		case R:
			node = new Node(tail.row, tail.col - 1, tail.dir);
			break;
		case D:
			node = new Node(tail.row - 1, tail.col, tail.dir);
			break;
		}
		tail.next = node;
		node.prev = tail;
		tail = node;
		size++;
	}
	public void addToHead()	{
		Node node = null;
		switch (head.dir) {
		case L:
			node = new Node(head.row, head.col - 1, head.dir);
			break;
		case U:
			node = new Node(head.row - 1, head.col, head.dir);
			break;
		case R:
			node = new Node(head.row, head.col + 1, head.dir);
			break;
		case D:
			node = new Node(head.row + 1, head.col, head.dir);
			break;
		}
		node.next = head;
		head.prev = node;
		head = node;
		size++;
	}
	
	public void draw(Graphics g) {
		if (size <= 0 )  return;
		move();
		for (Node n = head; n != null; n = n.next) {
			n.draw(g);
		}
	}
	
	private void move() {
		addToHead();
		deleteFromTail();
		checkDead();
	}
	private void checkDead() {
		if (head.row < 2 || head.col < 0 || head.row > Yard.ROWS || head.col > Yard.ROWS) {
			y.stop();
		}
		for (Node n = head.next; n != null; n = n.next) {
			if (n.col == head.col && n.row == head.row) {
				y.stop();
			}
		}
	}
	private void deleteFromTail() {
		if (size == 0) return; 
		tail = tail.prev;
		tail.next = null;
	}

	private class Node{
		int w = Yard.BLOCKSIZE;
		int h = Yard.BLOCKSIZE;
		int row, col;
		Dir dir = Dir.L;
		Node next = null;
		Node prev = null;
		
		Node(int row, int col, Dir dir) {
			this.row = row;
			this.col = col;
			this.dir = dir;
		}
		void draw(Graphics g){
			Color c = g.getColor();
			g.setColor(Color.black);
			g.fillRect(Yard.BLOCKSIZE * col, Yard.BLOCKSIZE * row, w, h);
			g.setColor(c);
		}
	}

	public void eat(Egg e) {
		if (this.getRect().intersects(e.getRect())) {
			e.reAppear();
			this.addToHead();
			y.setScore(y.getScore() + 5);
			
		}
	}
	private Rectangle getRect() {
		return new Rectangle(Yard.BLOCKSIZE * head.col, Yard.BLOCKSIZE * head.row, head.w, head.h);
	}
	
	public void keyPressed(KeyEvent e) {
		int key = e.getKeyCode();
		switch (key) {
		case KeyEvent.VK_LEFT:
			if (head.dir != Dir.R) 
			head.dir = Dir.L;
			break;
		case KeyEvent.VK_RIGHT:
			if (head.dir != Dir.L)
			head.dir = Dir.R;
			break;
		case KeyEvent.VK_UP:
			if (head.dir != Dir.D)
			head.dir = Dir.U;
			break;
		case KeyEvent.VK_DOWN:
			if (head.dir != Dir.U)
			head.dir = Dir.D;
			break;
		}
	}
}
